tavis



May 12, 1959 J. R. TAVIS GALVANOMETER STRUCTURE Filed Dec. 14. 1954 IN V EN TOR. JOHN R. TA W5 M& M

AT TORNEYS mm N m 0v 2,886,781 GALVANOMBETER srnucrunn John R. Tavis, Los Angeles, Calif., assignor, by mesne assignments, to Consolidated Elecurodynamics Corporation, Pasadena, (Zalih, a corporation of California Application December 14, 1954, Serial No. 475,130 Claims. (Cl. 324--154) This invention relates to improvements in the structure of galvanometers, and it has particular reference to arrangements for supporting the suspension system of a galvanorneter and for providing external electrical contacts for the suspension system located at the lower end of the galvanometer.

A typical galvauorneter comprises a suspension system which extends through the interior of the body of the galvanometer. "he suspension system comprises a light weight coil which is suspended by a pair of fine wires which are respectively anchored at opposite ends of the body of the galvanometer. A small mirror is atfixed to one of the suspension wires a short distance above the galvanometer coil so as to move in accordance with the deflection of the coil. A transparent window is provided in the galvanometer case adjacent the mirror for permitting incidence and reflection of a light beam at the mirror so that deflection of the coil is indicated by movement of the reflected light beam.

Ordinarily the upper end of the suspension system is connected to an external electrical contact located at the top of the galvanorneter, and the lower end of the suspension system is connected to the body of the galvanometer which serves as the other external electrical contact.

The use of the body of the galvanometer as one electrical contact causes the galvanometer to respond to stray electromagnetic and electrostatic fields, and it also requires that the galvanometer be insulated from its magnet mounting block. The insulating arrangement necessitates the use of a larger magnet structure than would be required if no insulation were employed.

The use or an electrical contact located at the top of the galvanometcr ordinarily requires a connector which is separate from the electrical connector which contacts the body portion of the galvanometer. Also. an electrical contact located at the top of the galvanometer makes it difficult to provide adjustments at the top of the galvanometer for controlling the tension on the suspension system and for controlling the angular position of the galvanometer coil in the magnetic field.

These difficulties are overcome in the present invention by providing both of the external electrical contacts for the galvanometer at the lower end of the galvanometer and by insulating both of the external electrical contacts from the body of the galvanometer. T he upper end of the suspension system is connected to a screw for adjusting the tension on the suspension system, and a rotatable sleeve is provided between the screw and the body of the galvanorneter for permitting angular adjustment of the suspension system without changing the tension on it. The adjustable sleeve is supported by a fixed conductive sleeve, and a conductive wire interconnects the fixed conductive sleeve and one of the electrical contacts at the lower end of the galvanometer so as to provide a connection to the upper end of the suspension system.

Application Serial No. 475,129, filed on the same date as the present application, discloses a similar arrange- Patented May 112, 1959 meat for providing external electrical contacts for the galvanometer at the lower end of the galvanometer.

The invention is explained in more detail with ref erence to the drawings, in which:

Fig. 1 shows an assembled galvanometer;

Fig. 2 is an enlarged, fragmentary, sectional view showing the details of the galvanometer structure; and

Fig. 3 is a sectional view along line 3--3 of Fig. 2.

The galvanometer comprises a body portion 10 of cylindrical shape. A suspension system 12 extends through the interior of the body portion of the galvanometer. The suspension system comprises an elongated coil 14 composed of fine wire, a light weight mirror 16, and a pair of fine wires 18 and 20 which support the suspension system and which provide electrical connections to the coil 14. A transparent window 17 is provided in the body portion of the galvanometer adjacent the mirror.

The upper wire it? of the suspension system is connected to a spring 22 which serves to provide tension on the suspension system. The spring is connected to a. conductive screw 24 which can be adjusted to control the tension on the suspension system.

The adjustable screw 24': is carried by a conductive sleeve as which may be rotated to adjust the angular position of the galvanorneter coil without changing the tension on the suspension system. That is, the suspension system may be rotated without changing the tension on it by rotating the sleeve 26 and screw 24 together as a unit within the body ill The tension on the suspension may be changed without rotating the suspension by holding the screw 24 still and rotating the sleeve 26. Preciseadjustment of the linearity of the galvanometer may be, efiected by adjusting the angular position of the sleeve 26; that is, the zero orientation of the coil can thereby be adjusted precisely so that the plane of the coil lies as nearly parallel as possible to the magnetic lines of force provided by a magnet mounting block for the galvanometer.

A fixed conductive sleeve 28 is disposed around the rotatable sleeve 26 and a fixed insulating sleeve 30 is located between the fixed conductive sleeve and the body of the galvanometer. The sleeves 23 and 30 may be cemented together and also to the body of the galvanometer.

The lower wire Ell of the suspension system is connected to a pin 32 which in turn is secured to an external contact member 34 by a screw 36. It will be apparent that the lower wire of the suspension system may be connected to the electrical contact in various other ways, such as by being soldered to a smaller pin which is secured to the electrical contact by a setscrew.

An annular-shaped electrical contact 38 is located above the electrical contact 34, and it is disposed concentrically. with respect to the longitudinal axis of the galvanometer. A pair of insulating members ill and 4-2 serve to insulate the two electrical contacts from each other and also from the body of the galvanometer.

The annular-shaped electrical contact 33 is connected to the upper end of the suspension system by a conductive wire 44 which inter-connects the annular-shaped electrical contact and the fixed conductive sleeve 28 at the upper,

end of the galvanometer. The conductive wire extends through an elongated glass insulator 46 which prevents the wire from shorting against the conductive body of the galvanometer and which provides a rigid guide for the wire so as to prevent it from becoming entangled in the ings, a tubular member 43 is provided inside the body asseyzsl of the galvanometer and the groove for accommodating the glass insulator is provided along the outer edge of the tubular member so that the glass insulator is located between the tubular member 48 and the body portion of the galvanometer. If desired, the tubular portion 48 may be an integral part of the body portion 10 of the galvanometer, and in that case the groove for accommodating the glass insulator is an internal groove.

It is desirable to provide a setscrew 50 for locking the screw 24 in position in the upper portion of the galvanometer. Also, a screw 52 may be provided at the top of the galvanometer for protecting it from dust and the like.

If desired, pole pieces 54 may be provided on opposite sides of the galvanometer coil 14 to increase the magnetic flux which acts upon the coil. Such pole pieces are composed of a magnetic material such as soft iron.

The body of the galvanometer and the other conductive members may be composed of brass. Preferably, the two electrical contact members are silver plated.

Thus, in the present invention the external electrical contacts for the galvanometer are located at the lower end of the galvanometer and both of the contacts are insulated from the body of the galvanometer. Adjustments for controlling the tension on the suspension system and for varying the angular position of the suspension system may be located at the upper end of the galvanometer since the electrical contacts are at the lower end. Hence, adjustment of the tension and of the angular position of the suspension system may be made while the magnet is located in its magnet mounting block.

For purposes of this disclosure and the following claims, the terms lower or bottom end of the galvanometer refer to that end of the galvanometer which is designed to be inserted into a magnet mounting block. The terms upper or top end of the galvanometer then refer to the opposite end of the galvanometer, that is, to that end of the galvanometer which protrudes from the magnet mounting block when the galvanometer is inserted into a magnet mounting block.

I claim:

1. In a galvanometer having a body portion in which a suspension system is located, the improvement which comprises means attached to the upper end of the suspension system for adjusting the tension on the suspension system, means coupled to the upper end of the suspension system for rotating the suspension system without changing the tension on it, an insulated conductor coupled to the upper end of the suspension system and extending through the interior of the galvanometer to the lower end of the galvanometer, an electrical contact extending around the lower portion of the galvanometer and connected to the conductor for providing an exterior electrical connection to the upper end of the suspension system, another electrical contact located below the first electrical contact and coupled to the lower end of the suspension system, and means insulating the two electrical contacts from each other and also from the body of the galvanometer.

2. In a galvanometer having a body portion in which a suspension system is located, the improvement which comprises a spring attached to the upper end of the suspension system, an externally threaded conductive screw attached to the spring, a rotatable conductive sleeve having internal threads engaging the external threads of the screw, a fixed conductive sleeve disposed around the rotatable sleeve, a fixed insulator sleeve located between the fixed conductive sleeve and the body of the galvanometer, an insulated conductor connected to the fixed conductive sleeve and extending through the interior of the body of the galvanometer to the lower end of the galvanometer, an electrical contact extending around the lower portion of the galvanometer and connected to the conductor for providing an exterior electrical connection to the upper end of the suspension system, another electrical contact located below the first electrical contact and coupled to the lower end of the suspension system, and means insulating the two electrical contacts from each other and also from the body of the galvanometer.

3. In a galvanometer having a body portion in which a suspension system is located, the improvement which comprises means attached to the upper end of the suspension system for adjusting the tension on the suspension system, means coupled to the upper end of the suspension system for rotating the suspension system without changing the tension on it, a glass insulator afiixed to and extending through the interior of the body of the galvanometer from the upper to the lower end of the galvanometer, a conductive wire coupled to the upper end of the suspension system and extending through the glass insulator to the lower end of the galvanometer, an annular-shaped electrical contact connected to the conductive wire for providing an exterior electrical connection to the upper end of the suspension system, the annular-shaped electrical contact being located adjacent the lower end of the galvanometer and disposed concentrically with respect to the longitudinal axis of the galvanometer, a second electrical contact located below the annular-shaped electrical contact and coupled to the lower end of the suspension system, and means insulating the two electrical contacts from each other and also from the body of the galvanometer.

4. In a galvanometer having a body portion in which a suspension system is located, the improvement which comprises means attached to the upper end of the suspension system for adjusting the tension on the suspension system, means coupled to the upper end of the suspension system for rotating the suspension system without changing the tension on it, the interior of the body portion of the galvanometer having a groove which extends from the upper to the lower end of the galvanometer, a rigid insulator located in the groove, a conductive wire coupled to the upper end of the suspension system and extending through the insulator to the lower end of the galvanometer, an annular-shaped electrical contact connected to the conductive wire for providing an exterior electrical connection to the upper end of the suspension system, the annular-shaped electrical contact the galvanometer located below the annular-shaped electrical contact and coupled to the lower end of the suspension system, and means insulating the two electrical contacts from each other and also from the body of the galvanometer.

5. In a galvanometer having a body portion in which a suspension system is located, the improvement which comprises a spring attached to the upper end of the suspension system, an externally threaded conductive screw attached to the spring, a rotatable conductive sleeve having internal threads engaging the external threads of the screw, a fixed conductive sleeve disposed around the rotatable sleeve, a fixed insulator sleeve located between the fixed conductive sleeve and the body of the galvanometer, the interior of the body portion of the galvanometer having a groove which extends from the upper to the lower end of the galvanometer, a glass insulator located in the groove, a conductive wire connected to the fixed conductive sleeve and extending through the glass insulator to the lower end of the galvanometer, an annular-shaped electrical contact connected to the conductive wire for providing an exterior electrical connection to the upper end of the suspension system, the annular-shaped electrical contact being located adjacent the lower end of the galvanometer and disposed concentrically with respect to the longitudinal axis of the galvanometer, a second electrical contact located below the annular-shaped electrical contact and coupled to the lower end of the suspension system, and means insulating the two electrical contacts from each other and also from the body of the galvanometer.

References Cited in the file of this patent UNITED STATES PATENTS Grabosch Mar. 19, 1901 

